1 files changed, 117 insertions, 0 deletions
diff --git a/src/projections/sterea.cpp b/src/projections/sterea.cpp
new file mode 100644
index 00000000..bb498068
--- /dev/null
+++ b/src/projections/sterea.cpp
@@ -0,0 +1,117 @@
+/*
+** libproj -- library of cartographic projections
+**
+** Copyright (c) 2003   Gerald I. Evenden
+*/
+/*
+** Permission is hereby granted, free of charge, to any person obtaining
+** a copy of this software and associated documentation files (the
+** "Software"), to deal in the Software without restriction, including
+** without limitation the rights to use, copy, modify, merge, publish,
+** distribute, sublicense, and/or sell copies of the Software, and to
+** permit persons to whom the Software is furnished to do so, subject to
+** the following conditions:
+**
+** The above copyright notice and this permission notice shall be
+** included in all copies or substantial portions of the Software.
+**
+** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+#define PJ_LIB__
+#include <errno.h>
+#include "projects.h"
+#include "proj_math.h"
+
+
+namespace { // anonymous namespace
+struct pj_opaque {
+    double phic0;
+    double cosc0, sinc0;
+    double R2;
+    void *en;
+};
+} // anonymous namespace
+
+
+PROJ_HEAD(sterea, "Oblique Stereographic Alternative") "\n\tAzimuthal, Sph&Ell";
+
+
+
+static XY e_forward (LP lp, PJ *P) {          /* Ellipsoidal, forward */
+    XY xy = {0.0,0.0};
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+    double cosc, sinc, cosl, k;
+
+    lp = pj_gauss(P->ctx, lp, Q->en);
+    sinc = sin(lp.phi);
+    cosc = cos(lp.phi);
+    cosl = cos(lp.lam);
+    k = P->k0 * Q->R2 / (1. + Q->sinc0 * sinc + Q->cosc0 * cosc * cosl);
+    xy.x = k * cosc * sin(lp.lam);
+    xy.y = k * (Q->cosc0 * sinc - Q->sinc0 * cosc * cosl);
+    return xy;
+}
+
+
+static LP e_inverse (XY xy, PJ *P) {          /* Ellipsoidal, inverse */
+    LP lp = {0.0,0.0};
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+    double rho, c, sinc, cosc;
+
+    xy.x /= P->k0;
+    xy.y /= P->k0;
+    if ( (rho = hypot (xy.x, xy.y)) != 0.0 ) {
+        c = 2. * atan2 (rho, Q->R2);
+        sinc = sin (c);
+        cosc = cos (c);
+        lp.phi = asin (cosc * Q->sinc0 + xy.y * sinc * Q->cosc0 / rho);
+        lp.lam = atan2 (xy.x * sinc, rho * Q->cosc0 * cosc - xy.y * Q->sinc0 * sinc);
+    } else {
+        lp.phi = Q->phic0;
+        lp.lam = 0.;
+    }
+    return pj_inv_gauss(P->ctx, lp, Q->en);
+}
+
+
+static PJ *destructor (PJ *P, int errlev) {
+    if (nullptr==P)
+        return nullptr;
+
+    if (nullptr==P->opaque)
+        return pj_default_destructor (P, errlev);
+
+    pj_dealloc (static_cast<struct pj_opaque*>(P->opaque)->en);
+    return pj_default_destructor (P, errlev);
+}
+
+
+PJ *PROJECTION(sterea) {
+    double R;
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
+
+    if (nullptr==Q)
+        return pj_default_destructor (P, ENOMEM);
+    P->opaque = Q;
+
+    Q->en = pj_gauss_ini(P->e, P->phi0, &(Q->phic0), &R);
+    if (nullptr==Q->en)
+        return pj_default_destructor (P, ENOMEM);
+
+    Q->sinc0 = sin (Q->phic0);
+    Q->cosc0 = cos (Q->phic0);
+    Q->R2 = 2. * R;
+
+    P->inv = e_inverse;
+    P->fwd = e_forward;
+    P->destructor = destructor;
+
+    return P;
+}
+